Question

During a drilling process, excessive drill wear and drill breakage may occur. As
an experienced machinist, you are required to investigate the probable causes
which lead to these problems and suggest on how to solve these issue.

Answer 1

In the solution to this question I will be covering right from the basic of the drilling process and conclude with the solution to question statement.

Drilling is a process of making holes on or through a material. Drilling can be done on a variety of materials starting from plastic, cement, metals, wood etc. Basically in the drilling process there are special drill bits for every material. They are preferred because they are each manufactured in a special way to be able to withstand the friction and other forces acting on the drill-bit during the activity.

During drilling, due to the high speed movement of the drill-bit through the drilled surface or material there is conisderable friction among the drillbit at the drilled surface. Now, if this process is being carried on in a proper way; the friction does negligible wear to the drill bit and the drill bit is manufactured keeping that in mind.

However, due to improper machining techniques there is excessive drill wear and sometimes drill breakage.

Following are a few points causing this issue and the corresponding cause and remedy :

1. Improper Drill bit selection - During a certain drilling activity if the selection of drillbit is done wrongly, it leads to either an inefficient drilling activity or cause excessive drill wear. Sometimes it may also cause drill breakage. Now a person may use a drillbit used to drill holes in wood to drill a hole in a concrete wall. Naturally the wood drill bit is not made to withstand the abrasion caused while drilling a hole in the concrete wall. This leads to excessive wear and sometimes leads to breakage. Morever the hole generated will be a rather ugly one too. Solution : Always select proper drill bit after confirming the material to be drilled and the drill bit material.
2. Improper drill speed. : This is also one of the major causes of drill bit breakage. There are at times while drilling through a thick slab of a material with a drilling machine which is not made to the drilling capacity of the required thickness. So the speed of the drill is slower than the speed required for the specific job of drilling. As a result halfway during the drilling process, the drill bit gets stuck nd eventually breaks sometimes getting stuck in the material causing a lot of trouble. Solution : Always use proper machines for specific dilling job requirements specially in case of bench drills.
3. Drill angle : During manual drilling operation due to unavoidable human error there are at times when the drilling machine is held at an angle that is not appropriate for the drilling process. In such cases when the operator starts drilling and then realises that the angle is different, he tends to correct the angle. This results to the drill getting stuck and breaking. Solution : Always make sure that the operator is holding the drilling maching at a right angle to the required job. Once activity is started, avoid making changes in the drill angle.
4. Unclamped/ moving/ unfixed job piece : There are instances in which the job is not fixed at a place during the drilling operation due to negligence or otherwise. In this case, during the drilling process, there is movement of the job and the job tends to get stuck onto the drill bit causing damage to the job of the bit and sometimes causing drill bit breakage. Solution : Always clamp/ fix the job before and while performing the operation.
5. Overuse of drill bit : Overusing any drill for a drilling operation without allowing the drill bit to cool leads to drastic wear in the drill bit. This happens because due to the high speed and friction the temperature of the drill bit increases too much and causes damange. Solution : Always allow the drill bit to cool after every job.